1. Field of the Invention
The present invention relates to a honeycomb regenerator for recovering a waste heat in an exhaust gas by passing the exhaust gas and gas to be heated alternately therethrough, which is constructed by stacking a plurality of honeycomb structural bodies each having a rectangular shape in such a manner that flow passages constructed by through-holes are aligned in one direction, and especially relates to the honeycomb regenerator used in a corrosive atmosphere.
2. Related Art Statement
In combustion heating furnaces used in industry such as a blast furnaces, an aluminum melting furnace, a glass melting furnaces or the like, a regenerator used for improving a heat efficiency, in which a firing air is pre-heated by utilizing waste heat of an exhaust gas, has been known. As such regenerators, Japanese Patent Laid-Open Publication No. 58-26036 (JP-A-58-26036) discloses a regenerator utilizing ceramic balls, and also Japanese Patent Laid-Open Publication No. 4-251190 (JP-A-4-251190) discloses a regenerator utilizing honeycomb structural bodies.
In the known regenerator mentioned above, at first an exhaust gas having a high temperature is brought into contact with the ceramic balls or the honeycomb structural bodies to store a waste heat of the exhaust gas in the regenerator, and then a gas to be heated having a low temperature is brought into contact with the thus pre-heated regenerator to heat the gas to be heated, thereby utilizing the waste heat in the exhaust gas effectively.
Among the known regenerators mentioned above, in the case of using the ceramic balls, since a contact area between the ceramic balls and the exhaust gas is small due to a large gas-flowing resistivity of the ceramic balls, it is not possible to perform a heat exchanging operation effectively. Therefore, there occurs a drawback such that it is necessary to make a dimension of the regenerator large.
Contrary to this, in the case of using the honeycomb structural bodies, since a geometrically specific surface thereof is large as compared with a volume thereof, it is possible to perform the heat exchanging operation effectively even by a compact body. However, in an actual industrial furnace, since use is made of a natural gas, a light oil, a heavy oil or the like as a fuel, a corrosive gas such as SOx, NOx or the like is generated. Moreover, in the aluminum melting furnace, the exhaust gas includes an alkali metal component or the like. Therefore, a catalyst carrier made of cordierite used for purifying the exhaust gas of an automobile as disclosed in JP-A-4-251190 has a drawback on anti-corrosive properties.
Further, in order to improve the anti-corrosive properties, Japanese Utility Model Publication No. 2-23950 discloses a regenerator utilizing alumina. In this case, since the entire honeycomb body is made of an alumina and an alumina has a high thermal expansion coefficient, there occurs a problem such that the regenerator is fractured due to a thermal shock if a heat cycle having a large temperature difference is applied thereto.